Selective system.



PATBNTED AUG. 28, 1906..

S. A. REED. SELEOTIVE SYSTEM.

APPLICATION FILED MAR. 13, 1903.

2 SHBETS-SHEET 1.

' 'PATENTED AUG. 28,1906.

S. A.'.REED.

SELECTIVE SYSTEM. Airuoumn 11.21) MAR. 1a, 1903.

2 SHEETS-SHEET Z.

u mm- ;sr tr-Es orrlcn connected therewith. I

ure 1 isa diagram of a simp 0 form of circuit.

- SYLVANUS ALBERT RE D, FQN EW QRKQY. Y.

s L crn/s srsrsm. Y

To mll whn m, it may concern:

'Be it'known that I,-SYI.vAnUsALBEa'r. REED, a citizen of the United States, residing in the city, county, and State of NewYork, have invented certain new and,useful Imthe following-is a specification. invention. relates to selective systemst-fi in w ich the selectionof a particular station" or apparatus out of severe in the sameycircuit is determined by the non-actuation. ofone of several electrically-operated devices associated therewith, and it also concerns] various other features andcombinations of features hereinafter explained in the s ecification and pointed outin the appended clizims', 1 Referring to theaccompanying drawings, which form a part-of this' s 'ecificatio'n, E1

involving-the selective feature of the present system and'illustrating the rinciple thereof; Fig. 2 shows diagrammatica ly an alternative; formjof central switching. apparatus forcon-' trolling the selection of stations,- as' hereinafter explained. Fig. 3 isa further modification or development of the selection-controb ling apparatus. ig. 4 illustrates theselect ivc system adapted to a telephone party-line, of the bridged magneto type, together .with animlication of the usual centre ollice apparatus and the selection controlling means" tion- .wherem necessary artificial resistance is made to serve a further usefulpurpose 'inthe. -d

actuation of parts of the apparatus. in Fig. 1, M andG are conductors joined at one end by a resistanccO, upon which at predelerlninml points along its length are.con-' tau-points a, b, c, and (I- Differential eleclronmgnets or selectors Z are connectednas shown in the figure, b'etween the conductors .\l and (Land the differential points of said elewn'onuigncis are connected witha common or return conductor N, which inthis figure lear'ls to one pole of thesource of current I], the other pole of which is provided with switching means K for making variable con: nection with any one of the points a, b, c, or d, as desired.- 1 .7

The dill'ercntial' magnets or selectors Z are located spectto their resistances from the conductors Specification of Patent. Application and Xarot 18,,1903.

sourceof current.

values at 'eachselector accordin lsistance l and l on 'eacli'side, an inalivalues may be determined by the variableconnecti'on of K with O but it is obvious fectl at all others;

responds .wi thv the nected with K, wil ,"and if anarm'ature is .it itwiil remain in its normal pos1tion, whi e all other selector-armatures will be actuated 1g. 5 is a modificasistancesl and in predeterminedpositions with re-- M and (i, so that each is connected with 'the Patented Aug. 28, 1906. "8- gl-ro;14.1 .eaa

' Mand G on either sideby proportionally different resistances. Thus the reslstance lon one side bears a different ratio to the resistance l' on the other side for each se- I e o ,nrovements in Selective Systems, ofwhich When contact is made at K with any one of the c'ontactoints a, b, c, or (1, current from tht source divides at that point into parts of, values inversely proportional to the resistances on eitherside; and the'divided currents pass in; arallelpalongthe courses M and G .mteiieac of the selectors Z and from thence .'to gthel common.

conductor N back tothe ljhe opposing. currents whichfenter I the selectors vary 1n relative.

to the retheir ori .point'on O can be found,at.whi'ch the current -will 'divide and produce equality of magnetic efl'ect at on'ese ector and an-unb'alanced efordinarily-operated b The selector Z, which coroint of the resistance con- I therefore be non-actuated,

h the re onderance of current in one of y ,P P H their. 001 s. 1

The selectorsZ may be differential electrochemical indicators or electrically-operated evices of any appropriate .type, and the re may, if preferable, be combined with or wholly constitute the differen- Inthe drawings, however, I

tiali windings have shown said windings as e ual and 0 pcsite'f eils connected, respective y, with and G in d'with the common return-conductor l\', and in Fig. 5 I have indicated a different methodof utilizing theresistances Z' and I. It is manifest that I am not'limitcd in' the number of selectors which may be connected with the conductors M and G and that an indefinite numberfof points, such as a b c, &c.-, can be found on the resistance 0, such that contact of K with one of them will cause the neutrality of one of said selectors and the simultaneeus activity of all of the others.

In the modification shown in Fig. 2 the conductors M and G-are respectively con nected -with like poles of sections H and H Q 529.429 m i of-the source of current, and the other poles are connected by the' resistance 0, upon whichithe predetermined -contact-points a b c, &c., may-be located, as beforefl The v'ariable connecting means K is connected directly with the conductor N.

- Contact of K with a point, such as b, for

exam le, causes current from the sections H. 2 to travel along the paths or courses and M and G; in aralleh-asbefo're, said currents meeting III t selectors from opposite directions, but with equal effect only at the selece tor at B and returning through the conductor N and the proportional parts of the'r'esistance 0 above andv below; oint b, respectively, to their sections of I; rent.

- In Fig. 3 1 have illustrated an arrahgement the source of current H- are connected, r'e-' spectively, with the conductors M' andG and the conductor N is provided with a sliding or other shiftablecontact Kay-whereby it,

' may be connected with predetermined pairsof contact-points a, 6 c, ord as shown in the drawings; The pairs of contacts just-re .ferred to are so arranged that when N is coir- 4 nected by means of K with one of them com-:'

pllementary amounts of the section's H? and are connected with'the-circuit, the 'remaining parts being tern orarily' unused; Current from the section Ti above the contact K traverses the conductor-M, and current from the section Hfbelo w the contact K traverses the conductor G, meeting the cur;

rent, as before, at the diil'erential points of the selectors, whence both currents pass through the conductor N to their respective sections of the source. The shifting or sliding contact Kis a sim- :ple means for determining the amount 'ofeach section of battery, which is connected to the conductors M and G, respectively, and these amounts are predetermined for each pair of contacts so that the relative currents in M and G will balance in one of the selectors and produce selective non-actuation, as de scribedin, connection with the foregoing figures, c

. Fig. 4 represents'the above-described sys; tem of selective control applied toa'polysta- 'tion line in which M and N are line conduc tors terminating in--line'-jack 'J and line-'signal-.

--J' at the central station. At each ofthc substations A, B, and l) a subscribers telephoneapparatus 'l is dis )o'scd in normally 0 on bridge connection withthe' conductors LP and N The selectors Z are dill'erential clec'tromagn etscomicctcd on one sifdei w'ith the conductor M through a resistance land e source of "cur ergi'zation 'of Y.

when extensions 3 and'block their movement to on the other side with the contactoint 2 through resistance 1, the resistances and 1 bearing a different ratio to each other at eachstation. 'Thcdiiferential points Z of said electromagnets are connected throu h polarizedrelays Y with the conductor h, which is thus the comh on return-conductor forlthe selectors Z as well as one side of the tele hone-line proper.

. earmatures Y of the relays Y may be constructed and arranged in any suitable manner-as, for example, as shown in my 4 prior patent, No. 688,118, December 3, 1901 They are polarized and have a normal bias due to their polarization toward the nearest pole'of the relay,vwhich.bias. causes them to per'sist'in the last position in which the current has placed them; but this bias ma of course be secured by mechanical means, i desired. The armatures Y are adapted to connect the contact-points z with the round when moved in onedirec'tion and to c ose the gap across contacts t t of the normally'open telel phone-bridge when moved in 'the other direction, an-i'nsulated contact-plate y being proivided'on the front face" of the armature for this'purposq'as shown in" the drawings. As the? arniaturemoves in the direction to engage contact-point 2 an extension 3 encoun t'ers the spring or yielding stop 3 which has jsuifici ent strength only to resist the force of the .bias of the armature and hold it out of.

con'tacflwith 2' when it is not positively moved into co ntactxw ith itby the proper enflheselectors'Z are also provided with armatures Z, normally held in an undefiected position by'means of springs or gravity and so disgosed withv respect to the relays that eflected they obstruct the paths of the close the telephone-bridges. The blocking of the extensions, however, takes place after they have passed the iniddlepoints of their strokes, so that their normal bias will hold them interlockedwith the extensions 1 until the latter are returned to their original )ositions by means ofthe relays Y. lt'wi I be observed that the extensions 1 are provided 'with pointed pro tremlties, exten ing to a position just in front of the ends of the deflecting mciribcrs Z when the rclay-armaturcs are in their norections or spurs at their cxinal orintermediate position, the pur use of this arrangement being to bring the re ay-armature virtually'as close-as possible to the blocking member 'and s'till to permit it to inove beyond its middle point when Z has been deflected. a

At the'station 'D, I have shown the tele "phone ap aratus T indetail for the purpose of more c c'arly illustrating the operation of the system, which will hereinafter described ;'.but it is ofcourse to he understood -that the subscribcrls telcphone apparatus may be connected with thesystem in various skilled in the art.

. M. The subscriber's magneto-generator 6 1n a casing and the armature Yfan dthe bolt- I ower mntiwt-point 2, conductor 3, switch .4,

hook is raised, the local'transinitter circu'it 7 subscriber that the line is busy.

d ill'erent ways'which will be obvious to those When the switch-hook Tiis depressed by, the weightpl the receiver thereon and the 'relay-armature Y has connected the contacts t 1, current from the line conductor N ma phss through conductor l,'switch-hook ringer 5, contact-points t ttto the conductor is adapted to be inserted in the circuit ,by means of the switch-key {1, or of course an" automatic switch-generator may be used without the switch '4.I When tl 1e i ece iveris closed, and the currentfrom the secondary 8 of the transformer may find its way to the line N through conductor 1 on one side and through the'receiver and contact-points t t on the other to line M. a i I I v Y Another means of connecting the telephone apparatus with the lineeondnetors M and N is provided, by which the subscribers may connect with the'line to initiate a, call at any time when the-lineis notv busy, as will be laterdescribeth This connection is efl'ected by means of the conductor 9, leading to a key 10 of conducting material, whiehis'ada'pted to enga ge a key or bolt. 1 1 whiclf in turn mar,- engage a contact-point 12,- eor'thecteduwit line conductor M. The armature Z is adapt-1: ed to block -the circuit-closing iiiovement of the bolt 11 in the samemanner it does the" relay-armatures ,Y so 'thatwhe'nan arma i ture Z is deflected-neither the =armature Y3: nor the. bolt 11 can be operatedito connect the telephone with the line. the purpose of simplification in the draw ngs I have indicated the bolt- 11. as blocked by a l-extension of the selector-armature; in actual ractice the selective appa'ratu "'s inclosed 11 are compactly disposed side side, en-; ga ing the single end of the arrnatufige Z.

f desired, a target X-may be secured to one of the movin r parts-such,; gif example, as y -to be visib ethrougll ,undow in the casing'when the armature is ih its blocked position, such condition indicating to the The central ollice comprises the usual plug and cord circuit, together with an operator's listening-in set, a disconnected signal ,S, brid ed across the strands M and N, and the usua switch-keys,-'which need not be here described. It is also provided with a selection-controlling apparatus capable of being applied to,-the line to supply oppcsingcurrents in predetermined proportions to the conductors M and the ground (i in the-manner described in connection .with Fig. 3, said opposing. currents returning through the common return-conductor l\'.- 1

.Upon the operation of the key It, while the describe. J

plu is inserted v the jack "J fthe leads" R an R are eonn'er'qted, respectively, with the 'conductoi'sMand N, and the s lta-ltionemtmlllng flzrparatus'associatedgwith saidleads' ism eon ition for operation. Instead of a shdmgcontact, asshown in Fig. 3, this switching apparatl'ls is provided for convenience and accuracy in mu m pulation with aseries of switch keys a, If, e" andYhf such as are common in telephone mnstruciqstion, one for each station on the warty-line; 'lfhe'source of current (represented tine'rally .5 by I l) .is dividedinto sections 'l l ant l.l -,'c(,invenientlshown 'on' eith'ersid e ol'the row of switch-keys. Thepositive olesol' predeter 8o mined elementsor'groupsji elemc'ents'of each section of the source oi' -current-ll arejeoirneeted with the movable spring members of the switch-keys, andthenegative olesof the intermediate elementsbfsec'tion 1 are con-'- 8 nectedLwith the inside fixed conta'ct-plointsoff' the switch ke s oironeside,'.as sliownin'thefl drawings, ,and theneg'ative" poles of. the elenients offlction H are cennectedwith-the in- .e

side fixedcontact points nf theswitch keys 0 V on the other side in the-seine"manner, exeept' that with the section MF-the negati ve poles 'are progressively connected withth'e next ad-j jacent'v switch'; on {the left-hand side, whilethose of section Harep' gres'siyely'conneigk 9 ed with the ad'ac'ent switch-key Anise; i

ri lit-handTside;' KT .efloutside' fixed contacts";v o theswitch keys are connectedwith seen: dueto'rorir pairof conductorsjP whichftei'f, minate in at mil ol contact-terminals 1), and v1 00 conductors hand 'P.lead,*respectivel frmn. the,.negatl \7epole ofiseetions ll ani llxto'f con et-terni'inalsand p. illllctmtacts 79 f p eenstitujtelthe ined ,terminals of the twosections ofthe battery, and their com mon ter- 1 05 minal is the air of contacts pp." 'lhese ter minals are at apted to be connected with the linewircuit. in either direction by means of the polechanger P, whichl. now proceed to I A longitudinally-lnovable shal'tQ ol' insulating material carries n ion it a pair of o mositel -i.-xtemling springingers Manda", mth of which are connected with the sliding con-3 tact-plate n and are adapted toengage, r 1S .spectively, with the contacts 7)" p and the pair of contacts 7) p. 'lhe shalt also carries insulated sprin -li ngers and m, 'respm tively,connectcllwith sliding (")llltP-t-Pltthh' g and m, and they are adapted to engage, respectively, withcontact terminals 7), p in} one position and with 1) inanother., 'l'hesliding contact-plates 1n'., n, and g are in wrmanent contact with brushes m, wL- antl q aud'a' handle 1" is confiI-cted with the shaft/ 25 Q to giveit the proper movement, so that the connections iii-[the hatter maybe. conven-- iently madefrev 'ersed,pntl hroken at the 0]), tioii oi'theoperator. I

The switch-keys a, &C., Il.l'( normally in 1 0 connecte then moves P in the direction of the arroig to apply the current of anentire section to one .which corresponds .with' station $11,. wherelg' the elements a 'bficii, and d iof section I which they receive opposing currents of prea east;

contact with-their inside contact-points, and when not 0 erated the'elements or groups of elements 0 '68.0h section ofthe battery are consecutively connected by them in series with one another with the'ne ative poles ofeach section connected with the contact-terminals. W3 as'already described. A's cial keyis also provided which Servesto, connect the positive pole of one of the sections to one of the contacts p p, and thereby the divided or parallel courses, for the purpose of unbalancing or operating all selectors. Instead of the battery elements a b", &c., and a" b", &c., I may-use a seriesof direct-cu rent generators or'a single generatorwith its. winding progressively'tapped." The 0 erators magnetoenerator -R. -i

5 between the leads "R, so that-i 1 may be utilized either. by the manualo'peration of a key', as shown,-or by means 'of an automatic switch in the well-known 'In'anner; but in any case. this generator and thatatthej subscribers station should be of the. pulsata.

in -.type and .of respective polarities. fwhich' wi 1 not disturb the appropriate.- positions of; the'polarized armatures of the relays Y. In describing the operation of the system I. will. assume" thatthe telephone. operator wishes to select. the subscriber; at, stati(")n'. l)

the key she depresses the. switch-key d f and element d" of section H .are connected with the common contactterminals p p.- She its primary. osition and current is applie the line, inc uding the relays Y- with-Hie -ap ropriate polarityto moveiallthearmatures g against-the tensions. of springs into-engagement with their contacts 2. Bothdifferential coils of the selectors are-thereby connected in the circuit betweenM and G, from determined proportions in t e following man- Current from the connected elements from section H.may pass from contact-ten minal 1) through the sliding contact .and brush m, flead R and plu to the line M and from thence'through the ifl'erent resistances I Z to the selectors. Curi'ent {10m eherfriilent ma ass from termina ,;t roug 'gerT and b i'ush g to the grouniit}, and from thence through resistances Z" to the selectors; where it joins with the other current and. asses through relays Y and conductor N to 'rush-..

connectd to theline when they are operated. "In the caseassumed the opposing current fror'nthe sections of H arrive-at the differen- -tial ldtromagnet at: station D with equal efiectsin'its core, andZ 'istherefore not deflect'e'd; but atall otherstations owing to the different?relativefvalues.of'l and I one current-'is preponderance, and the armatures Z'f are deflected into blocking positions. This :eondit n continues until by a further movement the poile-c'ha er in-the direction of t'he'-arrow the s ring ingers g sand m are .snappedsudde y into contact with termi ,nals .p pand spring-fingers a into contact "with terminal 4; and- '12, whereby the current in-the circuit is reversed, but the relai :tive proportions of thecurrent supplied, re-

spective to the conductors M and G pre-. :served unchanged. The relay-armatures respond tothis'reversal byv a rapid movement toward contacts it, which is necessarily accelerated by the tension of springs y and 'theground connections of selectors Z are at the same timeinterrupted at z.

.' The 2' contacts =23; are preferably following .contactsada ted to maintainthe ground connection-of se ectorsJZ' until thes urs on extensionsiy reachor pass the on s of armatures TZ', so, tliahth'e selecto r at station D is maintained in neutralizedor non-actuated condition .eve'nlafter the reversal of current.

VVhenfthe contact 2 is subse uently disc0n-' nected'" from the ound, t e selector of course becomes un alanced; -but before its armature- Z candeflect into blocking position he spur on extension y? will have passed beyond it, and'the contacts 't t at the station .D will be closed. At station D only has the telephone-bridge been closed and the other statlons'are effectively locked out of the line by means ofth'eir deflected selectors, which latter --also prevent the 'manual operation of ';the bolts' 11. Furthermore, the targets X at each non-selected 'station are moved into view and'indicate-the condition of-the line. The operator. may then release keygR and no longer needed, as the'bias of the relay-ar matures will" preserve the selccted and lockedout condition ofthe line.- She ma then converse witli'jthesubscriber at D t rough the cord-circuit "-or connect the line" with other'e';lines.--of 'the' exchange-Yin the usual mannen. :When the' conversation is fin- .ishedfthes operator manipulates the key R "and pole-changer? to reverse the'position of the relay-armatures and open'thetelephonecommunicate with the central oflice, he first the elements of each sectionare respectively ascertainsthat the-line is free by notici r theibusv signal and depresses key 10, whi ii .disconnectthe source of current H, which is brid e at station:'D,- -which also releases dr-un- -m{ in connection, reispectivil/y,

moves thc bolt 11 into contact with 12, which-closes his normally en telc honehridge to the line, and while oldingey depressed hc o ierates hisImagneto-gencrator 6,(and the key 4,) which delivers a pulsating current through the switch-hook T,

12, bolt 11, key N), connection 9,,ringer 5 key 4, hack to 6. Upon receiving the call the central operator connects the selectioncontrolling apparatus with the line and moves the po '-changcr to its primaryposition that is to say, with tlie sprin Jingers a incontact withterminals 1) anil g and with p and p, and she depresses key at the same time, which causes thc'eurrent from the whole section ll" of the battery to pass through the lead it, conductor M, throu 'h the upper coils of the selectorsjZ, relays and conductor N, causing the relay-armaturcs Y tomove in the direction of contact-' points z and connect the selectors with the ground. As none of the elements of-thesection ll", however, are connected in thecircuit by this operation, the opposing or lower.

coils of, the se ectors receive no current, and the sclmztorsjale consequently unbalanced and their armatures deflected into the block ing position at all-of the stations'onthe line, exceptat station D, at which the dellectin' member Z is held undcllcctcd by ihclm8\o the bolt or key 11-, which thesubscriber-is holding depressed. The operator ma .then rcvcrsethe current in the linc by a .mani ulation of the 'iole chan er and the described.

- the key subscriber, who thus has the exclusive use oi sum bec use of the selective non-bloc rclay-armatures move in the direction to close the telephone-bridge,as hcforc;'hut the bridge at station 1) is the only one that is.

closed, and the other substations are obviouslylocked out in the manner heretofore The operator maythen release it and ascertain the wants of the the line.

Should the subscriber at l) wishto connect with another subscriber on thesamc iartyline-such, for example, as (3- he hol tofnrtl traced, the relative values of these currents being ircdetermined to cause the action of all selectors except that at station (7. Upon the succeeding reversal of the current, as before, the rclay-armatures move to close lluielcphone-bridges and 'will be blocked therefrom at all stations except (3 and I) the king 7 ds his a key ll depressed while the operator again reverses the current-in the circuit by' means I and the other because ofthe manual blocking by-the bolt '11., -The=telephone'o crater then sends a riigipg-currentinto t e line conductors-M and which passes in; parallel through the ringers at both Cand .D and'in- "nect-sig'nal, which operates the drop S, the telephone operator may cause the relay-armatures -.to move away from the contacts t t, which movement unlocks the blocked selectors and also disconnects subscribers (J and -D.- -Upon withdrawing the plug'the relay-armaturesassume' their normal intermediatepositionsTesting against the springs y and t 0 line is ready for another' call. The

circuit S' f-for the purpose of short-circuiting {immediately after the drop falls any alterto enterthe sc ective line would tend to op 1 crate-thepolarized-matures Y.

1 'l'tunaycometimes be desirable to compli-' cate-the construction of relays Y by includanccs hadron either s de of the selectors. Such a construction is illustrated iii-Fig. 5, in which the location of the resistanccs will be readily? d iscerned "without special ex planation.' -=(2a'ro must betaken, however, that thescadded windings he of thc proper direction with respect tothe circuit, so that they will not-neutralize. 1 a

l lclaim -a.

I. Ina selective s stem a source of ourrent and a plurality 0 line conductors constituting parallel courscsior' the current, electrically-o crated devices connected betweensaid com uctors and-adapted to receive opposing currents from said courses, in combination with means-for varyin the strengths of current respectivelyt'to sair courses.-

2. In a selective system, a source of current and two line conductors constituting parallel courses for the current, electromotor devices connected between said mndiictors on one of them and ada itcd to receive opposing currents l'rolii-saiil courses, in' combination with means for varying the supply of current respectively to said courses.

3. in a selective system, a sourci ol' current and two liiic conductors constituting The switch-hook T' may obviously be mep depress disconnect-signal S is provided with a short ing in the r windings'thei roportional resistmrallel.courses for the current, in combine 7 dicatesl to' the one subscriber that he is 'Whe'n the subscribers have replaced their I receivers and have-given; the usualdisconnating'clearin out-'currcnt, which-if allowed FOO at different resistance distancesfrom a point s'eaise tion with differential selectors, connected conductors and selectors connected thereto tween said conductors and connections from the difierentialpoints of said selectors tothe tion with differential electromagnets con-' 7 source of current; means for'varyin the supg of current respectivel to sai courses, w ereby the efiectsof sai selectors may be selectively rendered neutral.

' 4. Ina selective-system, a source of cur rent and two line conductors constituting parallel courses for the current, in combi'nanected between said conductors, connections fromthe differential points of saidelectromagnets to the source of current, the said dif ferential pointskbeing located at proportionally-difl'erent resistancedistances from each of the said two conductors, and means for the sai -two courses.

supply of current respectively, 'tothe' said.

vary'i the supply ofcurrent respectively to v5. Ina selective system, a source of current and two conductors constituting parallel courses for the current, in' combination with a coil at each substation'connected to one of ssid'conductors and a corresponding coil connected to the other conductor, a common connection from each pairof coils to-jthe source ofcur'rent, and-means for varying the two courses, whereby the magnetic effects of the members of anyjpair of coils may be selectively balanced. v 6. In a polysta'tion telephone system,- a

source of current'and a circuit com rising parallel courses for the current,- se ectors and means control ed b the selectors for closing said bridges, in com ination with a source of current and a switching apparatus adapted to vary'the relative strengths of the currents respectively supplied -to the two line conductora" '8. In a polystation telephone system, a

source of current, two line conductors and a.

common return therefor, selectors connected between said line conductors fat proportionally-different resistance distances from each of then:I a telephone apparatus at a substa tances from said-selectors, a telephone a paratus at adapted to receive opposing currents from courses, telephone apparatus at the sub at pro 'ortionally difl'erentresistance disomjea'chof them, a common return a substation 'inanormally' open ridge from one of said conductors to the'common'return and means controlledb aselector at the substation for closingfsai bridge, in combinationwith a source ofcurrent at an operating station and a vanable connection of the same,

with the circuit.

10. In-a po'lystation telephone system, two

line conductors and a common return conductor therefor, a line-jack, differential selectoifs connected with all of said conductors and adapted to receive op osing currents, normally open tel ephone-bridges across two of said line conductors, and'means controlledby 'said selectors for closing said open bridges alncombination with a central-stationapparatus comprising a plug and cord circuit and connections to a source of current for controlling the relative porportions of-said opposing currents; I

1l.= In a selective system, a circuitincludting two line conductors and differential selecto'r's ada ted to receive opposing currents respective y therefrom and adapted to be oper-' atpd'by a'preponder'ance of one of said cur- ,rents a'line-jack for said circuit and a' plugcircuit adapted for connection therewith, a source of current in the plug-circuit and switching a aratus for varying therelative siirengthso the opposing currents.

- l2. In aselective system, a circuit compris- ;ing,two line conductors and a retum 'conduc-v tor'"therefor, difierentialselectors in the circuit and a line-jack connected with one of said line conductors and the return conduc-. tor,in combination with a plug and circuit; connection therefrom to a source of current and a variable connecting means associat with said source for controlling the propor tion of current respectively'supplied to said devices receiving opposin currents from the circuit, adapted to norma y block said armawas but to be non-blockin when said currents are equal in effect, an a switchi apparatus for controllin the proportions o cur-. rent supplied to the circuit whereby the electromotor devices may be selectivelyrender'ed non-blocking.

- -14. In a selective stem, a source of current and circuit inclu mg electromagnats and r amtures ada ted to be blocked 1n'combi-" nationwith di erential'electromotor devices [adapted to receivmgpposing currents from "the circuit and to'be operated by a preponderance of one of said currents to block said a'rmatures, and a switching apparatus for varying the relative strengths-f said opposing currents. '7 l 15. In a selectives'y'stem, a source of current and circuit therefor comprising parallel s courses -for'currcnt, elcetromagncts at the su'bst'ations in multiple relation to the circuit 'andprovided with armatures adapted to be "blocked in combination with electromotor' blocking means adapted to receiveopposing 10 currents 'fromsaid courses, and to be operat'cd by a preponderance of one of said currents, and means at an operating station for proportlonnig the current respectively an plied to said vparallel courses so that the bloc ctedstations. p 4

p 16. In a selective-system,two lin'e'con- .ductors and a common return conductor therefor, elcctromagnets at-the substations lsfm'ig'i means will be actuated only at the nonzo'jinmultiple relation to thecircuit having arjniatures ada ted to he'blocked, in combination with ill'erential, selectors connected with said line conductors at'proportiorrally- -'difl'crent resistance distances from each of them, and to said common return, a source of current and a variable connection between said source and the circuit for varying the- "line conductors.

' "current supplied respectively to said. two

' '17. In a seleetive system,-a source of curand circuit comprising divided paths for the current, differential selective devices adapted to be connected with said'paths toreeeive opposing currents therefrox'n, relays in the circuit for connecting said devices to the said paths, and switching apparatus for operating said relays and for varying the current supplied lj cspcctivolytosald paths. 18. In a selective-system, a source of cut- 40 rent andcireuit cdmprising divided paths'for the current, selective dcvn-es adapted to be connected with said paths to receive 0 posin currents therefrom, rcla'ys injmu ti lei re ation to the circuit for ci'mnecting said i e- 5 'vices to "the said paths, means for operating said relays, and a variable connection'for varying the proportions of current supplied respectively to said paths.

ii). in a selective system, a source .of current and circuit. comprising two line conductors, the same constituting, parallel courses for the current, selective devices adapted to receive opposing currents from said courses, relays for connecting said devices with the said two line conductors at pro mrtionally-- dillercnt resistance distances from each of them, means for operating said relays, and a variable connection for varying the proportions of current supplied respectively to said parallel cou'rscs. 1

.20. ln a selective systm'n, a source of current, a circuit comprising two line conductors constituting parallel courscsl'or the current, electronnagncts in multiple with the circuit having armaturcs adapted to he.

seq-12g i v 7 blocked, in combination with normally nonblocking electromotor devices for blockin' saidarmatures copnected between the saiil two line cond-uctorsat proportionslly-dillerent resistance distances from each of them,

and asswitching apparatus for supplying cu rrent to the circuit and var mg the current su pa o phed respectively to san two courses.

2]. In a polystation telephone system two -l coursesline'conductors constituting paral for the current, and a return 0on1luctor,'t'-lcphone apparatusat the stations, and relays or connecting thetclephonc apparatus to the circuit, andmeans for operating said rclaysh differential electromagncts connected to t e line conductors and the return conductor having armatures adapted, when dofiected,'toblock the relays, in combination with a source of current and switching apparatus at an opcrating'station for varying the current supp icd respectively to the said parallel courses, whereby said armatures may he deflected at the non-seleeted stations.

22. In a'polystation selective system, a circuit comprismgtwo'line conductors constituting parallel courses for the current and differential elec'tromagnetsfrela s in the circuit adapted to connect sai differential electromagnets with the said-two line conductors at fproportii'i'nally-difl'crent resistance om each. of them, and a'rcturn-' distances conductor in' combination with asource of current for operating said relays, and switching apparatus for varying the supply of said current respectively to the said parallel courses.

' 23. Ina polystation telephone system,two

line conductors, dili'erential electromagnets adapted tobe connected atthe-suhstatmns betweenone of said conductors and the ground, relays eonncctcdbetween the dill'er ential points-of said electrm'nagnets and the other conductor, armature-s for the dill'crential electromagncts and annaturcs for the relays adapted to be blocked by said lirstnamed amiaturcs, in Teombination with means at an operating station for selectively controlling the blocking action of said firstnamed arm'atuies. 4

.24. In a polystation telephone system, line conductors and subscribers iclelphone apparatus m normally open bndgcs t iereacross, a dlll'crcntial electromagnet for each hridge controllin theelosurc thereof and means for loo 3 tl sea 42a ture of which is adapted-to closeeit her the telephone-brid e or another connection,;a

spring yielding y holding said armature an rent divided into sections;

,intermediate position, and, a pole-changer .for reversing the current in saidrelays, in

combination with a diflerentialelectromagnet for blocking said relay, 'connected'in the circuitflby saidre'la and meansin! selec tively causing any ifi'erential magnet to be non-blocking 27. In a-se-lective system, a source of current, and a, circuit comprising divided'pathsl for the c'urrcnt and a return conductor. olari'zed relays in saidcircuit, and difierential selec'tors-adaptedto lie-connected in'said .cir-- v prising two line conductors an" differential cult by said rela s,. i n combination-with a pole-changer an switching apparatus ,-for varying the proportions of: current respectively supplied to said divided paths.

28: Ina selective system},a'sou'rce of current divided into j sections two line conductors supplied withcurrent'o'i the same polarity from said sections and a; commonreturn from said conductors, including axvariable connection with saidsections and the common return, whereby the proportions of the:

currents supplied :to each of saidconductors may be varied.; w v 29. In a selective system" asouiee of curtwo .lineconductors supplied-with current ofzthe same polarity from said sections, and 'ii-cominonreturn from said conductorsyeincludmg "a-fvaria'ble connection with said sectipn'snnd the com:

mon return, wherebj the proportions of the current supplied to each gifijsai'd conductorsmay be yaried and means for reversing the current in the circuit without changing said' proportions. v

30. A selectiVe-switchmg' apparatusjco'mprising" two sections of a source ofcurrent, and terminals connected respectively with like poles of said sections, a third terminal .and mcans-for'connectnig it with complementary' parts of each of-saidsections;

31; A selective switching apparatus comprising two sections of a source of current. and terminals connected tolike poles of said sections, a third terminal and switch'mechanisins for connecting the 'same with prede-. termined parts of said two sections, said parts when so connected being complementary to each other with respect to a'section of the source of current.

32. A selective switching apparatus, com- 26. In a polystation telephone'system,two

minal contacts adapted to be conneetedwith =coniplementary parts of each of said sections,

a movable member com rising=contact-fin gers adapted to'altei'nate y engage said two terminal contacts and said pair of contacts and conneetionsfrom said movable fingers to a linecircuit.

33. In a'polystation telephone system, two.

conductors constituting parallel courses for current, selectors adapted to receive opposing currents therefrom and a'common return from said selectors, an operating station comprising a current-source in two sections, each section being adapted'to be connected with one oi said conductors; a variable con nectionbetween the commonreturn and said sections whereby complementary parts of each section may be connected in the circuit to supply current to the parallel'courses in predetermined proportions; v

34.'.A polysta tion telephones stem, com

electro ets connccted-therebetween', a third con uctorconnected with the differential pointsof said electromag'nets, in combination with a source of current divided into sections having like poles respectively connected to the two first-namedconduc'tors and switching apparatusadapted to connect' 'said third conductor with, complementary parts of said sections. Y

- '35Q Inaselective system, two line cond'uci tors and differential electromagnets connected thereto and a cemmon return, relaysin cluded in the cir'cuit 'the windings of said rcla'ys compri ng artificial electrical resistanceon either si e of said differential electromag- -nets, and means for operating said relays and differential electromagnets 36. l'naselective' system, a relay-arma-. ture'; adapted to.'be blocked and a movable member for blockingthe same, a coil for actuating said blocking member adapted to be connected to the circuit b the said armature,

in combination with a fo lowing contact between thecoil and the armature, whereby a blocked or, a non-blocked conditionma' be assumed before the coil is disconnected om the circuit.

37. In a selective system, a selector one of whose terminals is'connected to a following contact, a member'for connecting said following contact to the circuit when moved in one direction, and an armature for the selector adapted to deflect, when saidconnection is broken, into the path of the movement of said member in the other direction.

' 38. he selective system, a'selector one of whose'terininals'is connected to a following contact a movable member for connecting said following contact to the circuit, and an 828fl29 statute for theseleetor ede tegito deflect In testimony whereef ir have hereunto into the path of movement 0 sezd movable signed my name in the preeence of two subw member, 111 eombinatwn with a projeetiqnpn scribing witnesses. eeld movable member extended to e posltmn 5 edjeeent the vend of said deflecting member, I SYLVANUS ALBERT REED wherebg' the movable member may pass be- Witnesees: yond t e middle point of its traverse when OeeAR W. JEFFERY.

the deflecting member is deflected. I H. G. KZMBALL. 

